Adsorptive Removal of Methylene Blue by Low-Cost Citrus sinensis Bagasse: Equilibrium, Kinetic and Thermodynamic Characterization

The potential of Citrus sinensis (mosambi) bagasse to remove methylene blue, a cationic dye, from synthetic solutions has been investigated in batch mode. Equilibrium and kinetics studies were carried out while varying the pH, biosorbent dose, biosorbent size, contact time and initial methylene blue concentration. The sorption equilibrium for methylene blue by C. sinensis bagasse was reached within 3 h at 30A degrees C. The sorption data was analyzed using pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. The sorption kinetics were found to follow a pseudo-second-order kinetic model. The maximum sorption capacity of C. sinensis bagasse was found to be 96.4 mg/g under optimum conditions. The equilibrium data in synthetic solutions were well described by the Langmuir isotherm model. The thermodynamic parameters, Gibbs free energy (Delta GA degrees), change in enthalpy (Delta HA degrees) and change in entropy (Delta SA degrees), for biosorption of methylene blue by C. sinensis bagasse were calculated to determine the feasibility of the process. A sorption-desorption study was also carried out using different eluents to determine the possibility of recycling the biosorbent.